Chronic diseases require administering of medicaments or drugs according to a pre-defined time schedule in order to keep the concentration level of a pharmaceutically active substance on a pre-defined level. Many medicaments require administration by way of injection by making use of syringes or syringe-like drug delivery devices. Such devices should be universally applicable and should be operable even by persons without formal medical training.
Moreover, such devices, like pen-type injectors should provide accurate, precise and reliable setting of a dose and subsequent dispensing of the respective medicament. Typically, the medicament to be dispensed and injected is provided in a disposable or replaceable cartridge, such as a vial, an ampoule or a carpule comprising a slidably disposed piston to become operably engaged with a piston rod of a drive mechanism of the drug delivery device. The drive mechanism is adapted to apply thrust to the cartridge's piston in distal direction in order to built-up a respective fluid pressure, which in turn leads to a dispensing of the liquid medicament via a dispensing or distal end of the cartridge being typically in fluid connection with a piercing element like an injection needle.
It is generally of importance, that the patient strictly follows a given prescription schedule. However, patients that already got used to the medicament for a long time or patients that suffer side effects of a chronic disease and which may be physically impaired, compliance of the prescription schedule is sometimes sub-optimal. Since a large variety of existing drug delivery devices is implemented all-mechanically, it is further rather difficult for an attending physician to control, whether the patient strictly follows the prescription schedule.
From document WO 2007/107564 A1 an electronic module is known, which is to be positioned on an outer surface of a pen-like medication delivery device. The electronic module is capable of measuring signals, such as audible, optical, vibration or electromagnetic signals, generated during operation of a pen-like medication delivery device. By way of detecting acoustic signals generated in response to setting of a dose of a medicament or generated in response to expelling a dose of the medicament, respective information can be gathered and stored in the electronic module, which allow to monitor frequent usage and operation of the drug delivery device.
Hence, the known electronic device may detect different “click-sounds” being indicative of a dose setting or of a dose dispensing procedure, respectively. However, such an electronic module is so far unable to precisely determine the size of a dose and the corresponding amount of the respective medicament dispensed from the device during an injection operation.
It is therefore an object of the present invention to provide an improved monitoring device allowing for contactless and quantitative determination of a dose set and/or to be dispensed by a drug delivery device. Moreover, the monitoring device should provide an elegant, reliable and precise approach to unequivocally detect and to identify one or more parameters, for example state parameters, or configurations of the drug delivery device, being preferably implemented in an all-mechanical way.